Disposable absorbent articles, such as sanitary napkins, catamenial pads, pantiliners, diapers, training pants, incontinent garments, and the like, are designed to be worn adjacent to a human body to absorb discharged body fluids. The body fluids can include urine, blood, menses and other excrements discharged by the body at various times, such as during a bowel movement or during a menstrual period. Such articles are normally multilayered in construction and include a liquid-permeable cover, a liquid-impermeable baffle and an absorbent positioned therebetween. The article can also include a transfer and/or distribution layer situated between the cover and the absorbent which directs body fluid downward, away from the cover and distributes the fluid in the x and y directions. The cover is designed to allow rapid transfer of body fluid down into the absorbent where it can be retained. The baffle serves to prevent fluid present in the absorbent from leaking out and soiling or staining an undergarment or another adjacent piece of clothing.
The body-contacting cover must serve many functions. First, the cover should provide a dry surface against the body of the user of the absorbent article. A measure of dryness is a low rewet value. That is, the cover should prevent rewetting of the user's skin when the absorbent article is compressed or distorted by ordinary body movement. This can be accomplished by placing a flow zone control layer beneath the cover, as taught in U.S. Pat. No. 4,908,026 issued to Sukiennik et al., or by forming uniquely shaped apertures in the cover, as taught in U.S. Pat. No. 3,929,135 issued to Thompson. Second, the cover should serve to mask the body fluid that has passed into the absorbent. This is especially true for feminine products where blood or menstrual fluid is being retained by the absorbent. Female users prefer a product having a clean appearance, and the presence of a blood stain could convey an impression that the product might leak or has to be changed immediately. Third, the cover should have sufficient openness (pore size distribution) to allow body fluid to pass quickly down into the absorbent. This can be accomplished by using a low weight material, using larger fibers with a higher denier, or by piercing or aperturing the cover. The use of a thin material, such as a tightly bonded fabric having a sufficient degree of wear resistance is also preferred. Fourth, the cover should be soft and comfortable against the user's skin. Portions of the user's torso, crotch, legs, thighs and buttocks may come in direct contact with at least a portion of the absorbent article. Fifth, the cover should be easy to manufacture, and lastly it should be relatively inexpensive.
Numerous prior art patents exist which teach different materials and constructions for the cover layer. The initial use of nonwoven materials has evolved into the use of one or more nonwoven fibrous layers, along with a film layer containing apertures. U.S. Pat. Nos. 3,945,386; 3,965,906; 3,967,623; 3,994,299; 4,014,341; 4,323,069 and 4,324,246 teach such combinations. Other patents, such as U.S. Pat. Nos. 3,888,254 and 4,675,013, teach the use of a cover layer which is laminated to other fibrous sheets. U.S. Pat. No. 4,762,520 teaches forming a cover from a carded fiber fabric containing melt fibers sub-divided into parallel streaks. Other U.S. patents, such as U.S. Pat. Nos. 4,710,186; 4,755,413; 4,798,604 and 4,806,411, teach forming apertures in the cover. U.S. Pat. No. 4,333,465 teaches a cover comprised of a liquid-impermeable composite material having a liquid-permeable zone. Lastly, U.S. Pat. Nos. 3,676,242; 4,690,679; 4,725,473 and 4,878,974 teach various methods of making film and fiber composite cover materials by coextrusion, laminating, etc.
Two patent applications filed by Kimberly-Clark Corporation, which relate to nonwoven webs, include U.S. Ser. No. 07/608,095, filed Nov. 1, 1990, by inventors H. K. Barnes et al., entitled "HYDRAULICALLY NEEDLED NONWOVEN PULP FIBER WEB and "U.S. Ser. No. 07/633,594, filed Dec. 21, 1990, by inventors C. Everhart et al., entitled "HIGH PULP CONTENT NONWOVEN COMPOSITE FABRIC."
Presently, some manufacturers are moving toward the use of two or more different kinds of materials for the cover in order to enhance the functionality of the cover layer. Published Japanese patent application 122,727 (1989) teaches a sanitary napkin which has a cover constructed of two different hydrophobic materials, both of which contain apertures. U.S. Pat. No. 4,285,342 issued to Mesek is somewhat similar except, instead of using two different kinds of materials, a large opening is formed in the cover layer of a diaper to enhance fluid flow into the absorbent. U.K. patent 2,124,907 issued to Lloyd teaches a fabric bonded to a water-impermeable material, with both materials located on the bodyside surface of the absorbent device.
In order for an absorbent article to exhibit improved fluid management, it should utilize one or more layers located between the cover and the absorbent. Such layer(s) should assist in keeping the cover dry by directing body fluid downward, away from the cover. The layers can also function to move the body fluid outward, in the x and y directions, so as to facilitate rapid fluid intake by the absorbent. U.S. patents, which teach the use of a fluid transfer or a fluid distribution layer beneath the cover, include U.S. Pat. Nos. 4,397,644; 4,480,000; 4,519,799 and 4,798,603. These patents teach various materials and compositions for the transfer or distribution layer which assist in directing the body fluid downward, into the absorbent.
Most of the cover materials described in the above-identified patents do not function as effectively as most consumers would prefer. Some covers exhibit a rapid fluid flow-through rate but have a harsh or irritating surface against the user's skin. Covers made from spunbond or carded webs are soft and comfortable but offer little in the way of dryness or fluid masking. Furthermore, some covers are difficult to manufacture and/or are expensive. Because of this, there is a need for a cover which is relatively inexpensive, easy to manufacture and which functions better than current, commercially available materials.
Now a bodyside cover has been invented which provides softness and comfort adjacent to a user's skin while having the properties of dryness, good fluid masking and rapid fluid transfer.